1. Field of the Invention
This invention relates to a p-type transparent electroconductive film.
2. Description of the Prior Art
Heretofore, there have been known transparent electroconductive films such as Nesa film (SnO.sub.2 thin film), ITO film (95 wt.% In.sub.2 O.sub.5 +5 wt.% SnO.sub.2), and the like, and these films have been produced by electron beam deposition, reactive sputtering, CVD (chemical vapor deposition) or the like. Among these films, Nesa film has been long used. Nesa film is advantageously chemically stable, but has drawbacks that the electric resistance is high and the light transmittance is not so high (about 80%). These two drawbacks have been solved by ITO film (e.g. see Japanese Patent Publication No. 19125/1975). Commercially available ITO films have a transmittance of about 90% and a sheet resistance of less than several tens .OMEGA./.quadrature..
However, these transparent electroconductive films are heated to a high temperature such as 400.degree.-500.degree. C. when produced, and it is not possible to produce them at low temperatures. Therefore, it is not possible to laminate a conventional transparent electroconductive film on an organic polymer such as polyester and the like.
A method for producing ITO films at low temperatures such as about 200.degree. C. by means of a reactive high frequency ion plating method has been recently proposed, but it is still difficult to produce the transparent electroconductive films at temperatures lower than 100.degree. C.
These transparent electroconductive films use a donor level due to oxygen vacancy and are all n-type (electron plays a main role of transferring charge). In case of photoelectro transducer and the like, if the transparent electroconductive film is formed at a p-type semiconductor side, the charge injection efficiency is disadvantageously lowered.